The invention relates to a knitting machine and a method to be carried out on said machine for producing knitwear which has stitches, especially from hard, inelastic thread material, using knitting needles and holding-down/knocking-over sinkers associated therewith.
The need for industrial textiles consisting of knitted fabrics or produced from same is ever increasing. This applies on the one hand also to knitted fabrics produced with knitting machines, especially circular knitting machines, on the other hand to products which are produced from hard thread materials which have little or no elasticity, such as for example metal wires spun from staple fibres, monofil continuous wires produced e.g. from copper or brass, or the like. A previously unavoidable disadvantage consists here in the fact that thread materials of this type can only be processed with difficulty on knitting machines and, especially at high processing speeds, frequently lead to the thread breaking.
Therefore there has already been known for a long time (DE-PS 516 317) a way of providing a rib circular machine for processing hard threads, in which the threads, before the actual stitch formation (sinking the loops), are preformed over additionally present holding-down and knocking-over sinkers to form loops. This preforming (preliminary loop sinking) takes place in that the knitting needles, after picking up the thread, are taken down into an intermediate position in order thus to lay or pull the threads over associated high sinker edges. Simultaneously with this, the sinkers are preferably raised in an opposite direction in order to carry out the preforming of the loops with the needles and sinkers together. Following this, the formed loops are transferred to the knocking-over edges of the sinkers, whereupon the usual stitch formation takes place by a further take-down solely of the knitting needles. Set against the advantage of the preparation of the stitch formation which is made possible by the preforming and which is gentle on the thread material, is the disadvantage that neither the length of the preformed loops nor the size of the formed stitches can be altered. Moreover no patterns can be produced.
The preforming of threads into loops is also generally known in the case of knitting machines for producing plush goods (e.g. DE 31 45 307 C2, DE 40 33 735 C2). The length of ground thread loops can here be made adjustable (e.g. DE 41 29 845 A1) in that the ground threads are laid over special drawing edges of sinkers and the sinkers are then pushed radially forwards to different extents with the aid of adjustable cams. On the other hand, the plush threads in the same machine are laid over the upper edges of the sinkers and are taken down to different depths by the knitting needles with the aid of adjustable cams. This results in a comparatively complicated machine structure which can admittedly be justified for the production of plush goods but would be much too expensive for the production of mainly monofil knitted goods produced from metal threads or the like.
In addition to this, methods and circular knitting machines suitable for carrying out same are known (DE 33 11 361 A1) which operate with the so-called relative technique and are distinguished in that the knitting needles and holding-down and knocking-over sinkers disposed between them carry out movements in opposite directions during the stitch formation (couliering, loop sinking). Thus on the one hand the use of less steep cams for the knitting needles and sinkers is possible. On the other hand, it is possible to work at greater speeds without there being the danger of thread breakage. In principle, therefore, such circular knitting machines should also be suitable for the gentle processing of inelastic threads. Moreover the additional advantage could be exploited that in the relative technique there is the possibility of forming stitches of differing lengths according to requirements and/or undertaking patterns (DE 33 48 030 C2, DE 34 33 290 C2, DE 39 28 986 C2). However, set against this is the disadvantage that knitting machines of this type do not make possible any preforming of the threads into loops.